The present invention relates to a knocking control system for an internal combustion engine, and more particularly to a knocking control system for controlling the knocking of an internal combustion engine while determining the most proper ignition position of the engine by the use of a microprocessor.
In the internal combustion engine of an automobile, a turbo-supercharged system has frequently been adopted in recent years so as to reduce the fuel consumption rate and improve output power, but the engine is made more liable to knock in the supercharged region as a result of the adoption of that system.
In order to obviate the knocking phenomenon, moreover, it is sufficient to retard the ignition timing. Retarding may be effected by adding a mechanism to the distributor to perform the retarding action in response to the pressure in the intake pipe of the engine even in the supercharged region. On the other hand, the knocking phenomenon is not only highly dependent upon the state of the engine but also innegligibily influenced by variations in the retarding mechanism of the distributor. If the distributor is intended to perform an ignition timing control function such as can satisfy all of the aforementioned points, the ignition timing is retarded more than necessary to make it impossible to achieve highly efficient running which is the intrinsic object of the turbo-supercharged system.
A knock control system is intended to improve the above problems. According to such a control system, the engine is equipped with a vibratory acceleration detector called a "knock sensor", by which the knocking state is discriminated to retard the reference ignition position signal of the distributor to a necessary extent so that the states of and variations in the engine and the distributor may be offset to determine the largest angular advance position that does not invite knocking. As described above, however, the knocking phenomenon is highly influenced by the conditions of the engine; such as the load state, the r.p.m., the air/fuel ratio, the intake moisture and the cooling water temperature of the engine. The system of the prior art, which has failed to take those respective conditions into consideration, effects control at a more retarded side than the most proper ignition timing so that it cannot achieve highly efficient running of the engine.